It is known, as disclosed in U.S. Pat. No. 4,161,219, to utilize a subsurface safety valve which is controlled from the well surface through a control line acting on a piston and cylinder assembly which controls a tubular member which in turn controls the movement of a valve closure member. The valve is normally biased to a closed position and is opened by applying hydraulic pressure in the control line. Such safety valves must be fail-safe, that is, they must fail in the closed position if any of the components in the valve fail. However, when the valve closes, due to an operating hydraulic control system failure, the well will become inoperative until workover or wireline operations occur. These may be time-consuming and expensive operations.
The present invention is directed to a dual hydraulic subsurface safety valve that utilizes two operating control systems. Therefore, if the primary operating control system fails, it can be disconnected and the secondary operating control system is utilized to continue the operation of the safety valve. However, the setting depth and operating pressures of the dual hydraulic valve do not vary from a standard single hydraulically actuated valve, and remains fail-safe.